Rtp/Udp/Ip Header Compression - Motorola 110502USM001 - Vanguard 60 Router User Manual

RTP/UDP/IP Header Compression

Introduction
What is a RTP/UDP/
IP Header?
Why Is RTP/UDP/IP
Header
Compression
Needed?
Vanguard Routing Model
T0100-01, Revision B
The Vanguard router can provide RTP/UDP/IP header compression on a link-by-link
basis. This section examines the options for RTP/UDP/IP header compression.
User Datagram Protocol (UDP) is a transport layer protocol that provides best effort
packet delivery on top of IP. As it is best effort service, UDP does not guarantee
reliable delivery. The Real Time Protocol (RTP) resides on top of UDP/IP and
provides fast delivery of real time traffic such as voice. Motorola's implementation
of VoIP uses UDP/IP or RTP/UDP/IP protocols to carry packetized voice.
Packetized voice is encapsulated into IP packets before being transported over an IP
network. In encapsulating the packetized voice, RTP, UDP and IP header
information is added to the packet to provide information on how the IP packet is to
be the routed through the IP network. This RTP/UDP/IP header information is
typically 40 bytes in size. This is a relatively large overhead considering that an
average voice packet is approximately 64 bytes. Comparing the encapsulated data
payload and voice payload shown in Figure 2-16, the 40 byte RTP/UDP/IP header is
a significant overhead when it is applied to the voice packet. The motivation for
compressing the RTP/UDP/IP header is to reduce overhead and bandwidth usage.
40 Bytes
IP UDP RTP
40 Bytes
IP UDP RTP Voice Packet
Figure 2-16. Encapsulated Data Packet and Voice Packet
RTP/UDP/IP Header Compression
2048 Bytes
Data Packet
64 Bytes
2-25
Release 5.4